Zeolites of the molecular sieve type have commonly been employed in cleaners, particularly laundry detergent compositions, as a builder to provide a water-softening function when the detergent or cleanser is placed in an aqueous solution.
Although useful with a wide variety of cleanser or detergent compositions including a variety of co-builders, zeolites have more recently been employed to replace phosphate builders. The undesirability of phosphate compounds in detergents or cleaners, because of their adverse effect on the environment, is also well known to those skilled in the art.
The use of zeolites as builders in detergent compositions has been described in a number of references, including U.S. Pat. No. 4,231,887 issued Nov. 4, 1980 to Denny, et al. and U.S. Pat. No. 4,605,509 issued Aug. 12, 1986 to Corkill, et al. Zeolite-containing detergent compositions are also disclosed, for example, in a co-pending U.S. patent application Ser. No. 07/328,274, filed Mar. 24, 1989 by Stephen B. Kong, et al., entitled "High-Carbonate Detergent with Decreased Calcium Salt Deposition", under common assignment with the present invention. These references are incorporated herein as though set forth in their entirety in order to provide a further disclosure as to the use of zeolites as builders in detergent compositions.
As a general consideration, zeolites have been found to be relatively expensive and/or difficult to employ in detergent compositions for a number of reasons. Initially, zeolites tend to be incompatible with certain common detergent components such as sodium silicate, particularly in solution and under high temperature conditions. These problems of incompatibility have been discussed for example in U.S. Pat. No. 4,243,544 issued Jan. 6, 1981 to Taylor and U.K. Patent Specification 1 568 420 published May 29, 1980. The references also discussed exemplary techniques for avoiding or overcoming zeolite incompatibility with silicates. However, such techniques were also found to be relatively complex and/or expensive as noted above.
Difficulties arising during manufacture of detergent compositions with zeolite, as noted above, have often been related to particle size of the crystalline zeolites. Typically, the zeolites have a particle size of approximately 1-20 microns. Thus, if the zeolite is used in its normal state with such a particle size, it commonly presented problems of dusting or segregation in the detergent composition.
For this reason, it has been found to be generally desirable in prior practice to agglomerate the zeolite either by itself or with other components prior to combination with the detergent composition or to be agglomerated in combination with the other detergent components.
The Denny, et al. patent noted above disclosed one technique of this type wherein zeolite was combined with relatively large amounts of an ethoxylated linear alcohol and sodium citrate to form "a matrix" for the zeolite. Although this technique formed a granular zeolite which was satisfactory for its purpose, it was relatively expensive and the relatively large amounts of materials required to form the matrix limited either the amount of zeolite or the amount of other constituents in the agglomerate.
Probably a more common technique employed in the past for forming granular zeolite involved spray-drying or similar drying techniques where the zeolite was initially formed into a slurry with a large liquid component. Such techniques produced generally satisfactory characteristics and also permitted combination of other components with the zeolite. However, these techniques were based on spray-drying or the like, and tended to be expensive, particularly because of the large energy requirements for removing the substantial water or liquid component during formation of the agglomerates. Furthermore, spray drying tended to produce a low density product, unlike the present invention.
Techniques of this type were disclosed for example by U.S. Pat. No. 4,243,545 issued Jan. 6, 1981 to Campbell, et al. That patent disclosed a detergent product with zeolite and silicate builders prepared by spray-drying.
U.S. Pat. No. 4,707,290 issued Nov. 17, 1987 to Seiter, et al. similarly disclosed a spray-dried granular adsorbent for adsorbing liquid ingredients for detergents. U.S. Pat. No. 4,096,081 issued June 20, 1978 to Phenicie, et al. disclosed particles formed from aluminosilicate, sodium sulfate and polyethylene glycol, initially with about 40% water, by spray-drying, the particulate formed by the above process further being combined with a spray-dried granular detergent product for use as a cleanser. The Taylor patent referred to above also described substantial amounts of water or liquid required in such spray-drying techniques for forming zeolite particles.
U.S. Pat. No. 4,379,080 issued Apr. 5, 1983 to Murphy also disclosed a granular detergent composition including zeolite as well as other solid and liquid components which were combined with a film-forming polymer soluble in an aqueous slurry. The combination was dried, by "spray-drying, flash-drying, microwave or oven drying" in order to form dried granules. U.S. Pat. No. 4,528,276 issued July 9, 1985 to Cambell disclosed the formation of agglomerates of zeolites and silicate by addition of water and application of heat, with tumbling, for use in detergent products.
A substantial number of other references similarly discussed the formation of granular zeolites by spray-drying. However, the reference noted and briefly discussed above are believed to be typical of those references, at least for purposes of the present invention.
It is to be noted that techniques other than spray-drying and the like, similarly requiring relatively high liquid or water input, have also been employed for forming granular zeolites.
U.S. Pat. No. 3,609,088 and U.S. Pat. No. 3,597,361 both issued to Sumner disclosed the use of a rotating drum for tumbling components in an agglomeration zone to form "a falling curtain of particles" to which an aqueous binder such as silicate solution or the like could be applied. The combination of the binder and the tumbling action of the rotating drum was found to result in satisfactory formation of agglomerated detergent products relatively high in phosphates and silicates with either aqueous sodium silicate or alkyl aryl sulfonic acid as a binder.
U.S. Pat. No. 4,414,130 issued Nov. 8, 1983 to Cheng also disclosed agglomerates formed from zeolite, a water soluble binder, preferably starch, and a small amount of water "by tumbling".
Although such references disclosed or suggested the formation of zeolite agglomerates by techniques other than spray-drying and the like, it remains important not only to assure that the agglomeration technique is relatively simple and inexpensive but also to assure that the agglomerates formed by the process have desirable physical characteristics such as uniform particle size, high density, hardness to resist fracture, good dispersibility, flowability, etc.